Maybe it would be better to have a long-running process watch the log. You can use File::Tail to read the log as it's written and note when a "STATUS = SUCCESS" line happens. When one comes in, set an alarm (alarm 30 * 60), which will reset any earlier alarm you set. When an alarm goes off , you know that 30 minutes have gone by without a success line, and you can take whatever action you like.